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1.
Amy E. Clifton Carolina Pagli Jna Finndís Jnsdttir Kristjana Eythorsdttir Kristin Vogfjr 《Tectonophysics》2003,369(3-4):145-154
Three large earthquakes (Mw>4.5) were triggered within 5 min, 85 km west of a Mw 6.5 earthquake in the South Iceland Seismic Zone (SISZ). We report on surface effects of these triggered earthquakes, which include fresh rupture, widespread rockfall, disrupted rockslides and block slides. Field data confirm that the earthquakes occurred along N-striking right-lateral strike-slip faults. Field data also support the conclusion from modeling of InSAR data that deformation from the second triggered event was more significant than for the other two. A major hydrological effect was the draining of water through an open fissure on a lake bed, lowering the lake level by greater than 4 m. Field relationships suggest that a component of aseismic slip could have been facilitated by water draining into the fault zone. 相似文献
2.
A.V. Lukhnev V.A. San’kov A.I. Miroshnichenko S.V. Ashurkov L.M. Byzov A.V. San’kov Yu.B. Bashkuev M.G. Dembelov E. Calais 《Russian Geology and Geophysics》2013,54(11):1417-1426
Based on multiyear measurements of present-day motions in the central area of the Baikal rift system, new data on the kinematics of horizontal motions, relative horizontal deformation rates, and rotation velocities in the area of junction of the South Baikal, North Baikal, and Barguzin rift basins have been obtained. This area is an intricate structure with two transfer zones: Ol’khon–Svyatoi Nos and Ust’-Barguzin.It is shown that crustal blocks are moving southeastward, normally to the structures of transfer zones and at an acute angle to the Baikal Rift strike, which corresponds to the right-lateral strike-slip extensional faulting along the major structure. The average horizontal velocities increase from 3.0 mm yr–1 in the northern South Baikal basin to 6.5 mm yr–1 in the Barguzin basin. The elongation axes prevailing in the study region are mainly of NW–SE direction. The areas of intense deformations are confined to structures with high seismic activity in the South Baikal and, partly, Barguzin basins. This confirms the existence of a present-day zone of the Earth’s crust destruction in the Baikal rift system, which is the most likely source of strong earthquakes in the future. Two zones with rotations in opposite directions are recognized in the rotation velocity field. Clockwise rotation is typical of structures of N–NE strike (Maloe More basin, southern North Baikal basin, Barguzin Ridge rise). Counterclockwise rotation is determined for NE-striking structures (northern South Baikal basin, southern Barguzin basin). In general, the obtained data show an intricate pattern of present-day horizontal dislocations and deformations in the area of junction of NE- and N–NE-striking rift structures. This suggests left- and right-lateral strike-slip faults, respectively, within them. 相似文献
3.
桐柏-大别南缘变质流体变质-变形特征及构造意义 总被引：1，自引：0，他引：1
前人研究认为桐柏山主要是由桐柏核部杂岩单元组成,它是一个早白垩世花岗质片麻岩杂岩体,其中包含一定的三叠纪中高级变质岩石,后期一起经历相同的构造变形过程,在南北两侧形成剪切旋向完全相反的两条大型韧性剪切带,殷店-马垅剪切带就是南边的华南板块由SSE→NNW挤压作用下,在斜切大别造山带的方向上产生的右行平移断裂带。在野外进行地质考察的过程中,发现在该地区变质流体的分布具有一定的规律。因此,本文通过对殷店-马垅剪切带地质特征、走滑性质、糜棱岩及糜棱岩化岩石的变质变形,剪切带内长英质脉体物质组成、变形特征及物质来源等方面研究,探讨剪切带中变质流体的分布规律以及变质变形与变质流体之间的关系。 相似文献
4.
Pietro Passerini Marta Marcucci Giovanni Sguazzoni Leonardo Zan Abdourahman Omar Haga 《地学学报》1991,3(6):607-618
Slickenside studies in regions of crustal spreading such as Iceland and the Afar Depression, East Africa, reveal that a significant number of faults parallel and close to rift axes are strike-slip rather than normal. Therefore, the pattern of brittle deformation in these regions does not conform to the classic two-dimensional schemes of oceanic tectonics and pre-oceanic rifting. Dip-slip and strike-slip faulting presumably alternated along or in the vicinity of spreading axes, indicate a varying stress field and a combination of transverse and longitudinal movements. In Iceland, strike-slip faults parallel to rifts are observed both west and east of the rift system as well as in a median area between overlapping rifts; the mechanisms proposed for their origin include accommodation of oblique convergence or divergence of crustal sections due to variations of spreading directions along axis and the interaction of overlapping rifts. In the Afar Depression this kind of fault is recorded west of the rift of Asal and can be imputed to reflect an interaction among rifts in the vicinity of the Afar triple junction. Rift-parallel strike-slip faults cannot however be assumed to be a feature of all crustal spreading axes due to the peculiarity of the examined regions: both of them are hot-spot areas and the Afar Depression lies at a triple junction. 相似文献
5.
AbstractThe South Iceland Seismic Zone (SISZ) is located at the junction of three rift segments in southwestern Iceland. The presence of different types of faulting and of differently orientated subgroups in Upper Pliocene to Holocene formations indicate polyphase tectonism. We measured 736 minor faults at 25 sites. Two types of relationships between stress regimes are represented. The first type, named IDS (inhomogeneous data set), is characterized by the presence of two types of fault mechanisms, normal and strike-slip, consistent with a single direction of extension. The second type, named OSR (opposite stress regimes), is characterized by the presence of perpendicular directions of extensions for a single type (normal or strike-slip) of faulting. Because of contradictory chronological criteria, we infer that the OSR alternated during the brittle tectonic activity of the SISZ. Two stress regimes, primary and secondary, are characterized by directions of extension NW-SE and NE-SW, respectively. The general fracture pattern characterized for the primary stress regime in the SISZ includes NNE-SSW trending right-lateral strike-slip faults, conjugate ENE-WSW trending left-lateral faults and NE-SW normal faults. This distribution is quite consistent with a Riedel- type model of fault pattern in a left-lateral shear zone. The stress states characterized based on analysis of both the earthquake focal mechanisms and the recent faulting sow great similarity in terms of stress directions. The main difference is the larger ratio of strike-slip motions representing 71% of the total population in the case of earthquake focal mechanisms, whereas for the whole set of faults the proportion of strike-slip faulting was 50 %. We explain that a témpora evolution of the tectonic regime in the SISZ region, accompanied by a gradual change in stress field, starts with rift-type pure extension and progressively leads to development of preferentially strike-slip structures in the kinematic context of left- lateral transform motion. © Elsevier, Paris 相似文献
6.
In the Himalayan chain the collision of India into Eurasia has produced some of the most complex crustal interactions along the Himalayan–Alpine Orogen. In NW Bhutan, middle to late Miocene deformation has been partitioned between conjugate strike-slip faulting, E–W extension along the Yadong-Gulu graben and kilometre-scale folding. To better understand the late deformation stages and their implications for the evolution of the eastern Himalayas, the palaeomagnetism in the erosional remnant of the Tethyan Himalayan rocks outcropping in NW Bhutan has been studied. Their position to the south of the trace of the inner South Tibetan Detachment, to the south of the Tibetan Plateau offers a unique possibility to study the Tertiary rotation of the Himalayas. Pyrrhotite is the carrier of the characteristic magnetisation based on 270–325 °C unblocking temperatures. The age of the remanence is ca. 13 Ma indicated by illite 40K/40Ar cooling ages and a negative fold test. Small circle intersection method applied to the pyrrhotite components shows a ca. 32° clockwise rotation with respect to stable India since 13 Ma. We suggest that this clockwise rotation is related to strain partitioning between NE-directed shortening, sinistral-slip along the Lingshi fault, and east–west extension. This represents a field-based explanation and a minimum onset age for present-day eastward motion of the upper-crust of SE-Tibet and NE-Himalayas. 相似文献
7.
《Geodinamica Acta》1999,12(5):303-319
The South Iceland Seismic Zone (SISZ) is located at the junction of three rift segments in southwestern Iceland. The presence of different types of faulting and of differently orientated subgroups in Upper Pliocene to Holocene formations indicate polyphase tectonism. We measured 736 minor faults at 25 sites. Two types of relationships between stress regimes are represented. The first type, named IDS (inhomogeneous data set), is characterized by the presence of two types of fault mechanisms, normal and strike-slip, consistent with a single direction of extension. The second type, named OSR (opposite stress regimes), is characterized by the presence of perpendicular directions of extensions for a single type (normal or strike-slip) of faulting. Because of contradictory chronological criteria, we infer that the OSR alternated during the brittle tectonic activity of the SISZ. Two stress regimes, primary and secondary, are characterized by directions of extension NW-SE and NE-SW, respectively. The general fracture pattern characterized for the primary stress regime in the SISZ includes NNE-SSW trending right-lateral strike-slip faults, conjugate ENE-WSW trending left-lateral faults and NE-SW normal faults. This distribution is quite consistent with a Riedeltype model of fault pattern in a left-lateral shear zone. The stress states characterized based on analysis of both the earthquake focal mechanisms and the recent faulting show great similarity in terms of stress directions. The main difference is the larger ratio of strike-slip motions representing 71 % of the total population in the case of earthquake focal mechanisms, whereas for the whole set of faults the proportion of strike-slip faulting was 50 %. We explain that a temporal evolution of the tectonic regime in the SISZ region, accompanied by a gradual change in stress field, starts with rift-type pure extension and progressively leads to development of preferentially strike-slip structures in the kinematic context of leftlateral transform motion. 相似文献
8.
陕西凤太矿集区多金属成矿作用的构造控制 总被引：3，自引：0，他引：3
陕西凤县-太白(简称凤太)矿集区铅、锌、金、银、铜多金属资源丰富,已发现二十余个大中小型矿床。在大地构造位置上,凤太矿集区位于南秦岭造山带北缘,紧邻商丹缝合带。以往的工作缺乏对矿集区整体的构造研究,本次工作通过比较系统的构造测量和解析,提出在南秦岭晚三叠世碰撞造山过程中,凤太矿集区南北两条边界断裂带的左行走滑运动导致在区内衍生了NNE向主压应力场,从而形成了NWW向复式褶皱、脆韧性剪切带、断裂和节理(纵向破裂)、B型线理,以及NNE向断裂和节理(横向破裂)、劈理、张裂隙等一系列构造组合,所有构造形迹都是在统一构造应力场下随着构造层次不断抬升,脆韧性和脆性递进变形叠加的产物,共同构成了一个大型压扭性走滑双重构造变形系统。在构造几何学上,凤太矿集区整体上表现为一个隔档式复式褶皱,由一组NWW向紧闭复背斜和一组相对宽缓复向斜组成。区内的多金属成矿作用、岩浆活动、动力变质变形作用的同位素年龄数据集中于230~190Ma。综合地质演化和成矿作用的研究成果,提出在南秦岭碰撞造山过程中引发的动力变质变形作用和岩浆活动提供了成矿元素和成矿流体,在温压梯度以及浮力效应的驱动下向上运移至走滑双重构造变形系统中的有利扩容空间中发生充填型和交代型矿化,即凤太矿集区多金属矿床是区域大规模变形变质-岩浆活动-流体作用的产物,是在构造作用这一主导因素控制下形成的一个多金属后生热液成矿系统。 相似文献
9.
柴达木盆地东北部新近纪构造旋转及其意义 总被引：4，自引：1，他引：3
青藏高原东北缘构造变形的研究是认识高原隆起过程、机制和印度—欧亚板块碰撞远程效应的重要途径。柴达木盆地是印度－欧亚板块碰撞后南北向挤压应力为动力背景的高原东北部内陆盆地,沉积物主要来自于周边山地,完整的保存了新生代以来高原隆升的详细记录。通过柴达木盆地东北部瑙格剖面精细古地磁及构造旋转研究发现,20.1～15.1Ma以及15.1～8.2Ma柴达木盆地分别发生了9.7°±7.4°和6.4°±4.4°的顺时针旋转,约8.2Ma后,柴达木盆地东北部瑙格地区发生了16°±7.5°的逆时针快速旋转。通过分析认为,前两次的顺时针构造旋转事件可能与阿尔金断裂的左旋走滑有关。而约82Ma以来的逆时针旋转事件属于柴达木盆地东北部瑙格地区的局部旋转,可能与温泉断裂的右旋走滑有关,说明青藏高原东北部在昆仑山、阿尔金山和祁连山三条巨型断裂系左旋相对运动的宏观控制下形成的NNW向温泉右旋走滑断裂开始走滑的年代为约8Ma。 相似文献
10.
Daniel A. Gregori Jose Kostadinoff Guillermina Alvarez Ariel Raniolo Leonardo Strazzere Juan C. Martinez Mercedes Barros 《地学前缘(英文版)》2013,4(6):693-708
The Preandean geological configuration of the eastern North Patagonian Massif is established through the use of geological and geophysical analysis.The positive gravity anomalies located near the Atlantic coast are due to 535 and 540 Ma old rocks belonging to the Pampean Orogeny （Precambrian-middle Cambrian）,which are widely recognized in central and northern Argentina.The Famatinian Cycle （Ordovician-Devonian） is represented by a Silurian-Devonian marine basin equivalent to those of eastern-central Argentina and South Africa,and which was deformed at the end of the Devonian byan～E-W to WNW-ESE compressional event,part of the Famatinian Orogeny.Containing strong gravity gradients,the NW-SE belt is coincident with fault zones which were originated during the Gondwanide Orogeny.This event also produced NW-SE overthrusting of the Silurian-Devonian sequences and strike-slip faults that displaced blocks in the same direction.This deformation event belongs to the Gondwanide Orogeny that includes movements related to a counterclockwise rotation of blocks in northern Patagonia.The strong negative anomalies located in the western part of the area stem from the presence of rocks of the Jurassic Ca（n）adón Asfalto basin interbedded in the Marifil Complex.These volcaniclastic sequences show mild deformation of accommodation zones in a pre-Jurassic paleorelief. 相似文献
11.
12.
B. I. Ikhsanov 《Moscow University Geology Bulletin》2011,66(2):137-141
This paper describes the structure and the principal evolutionary stages of the Ushakov postdeposition anticline zone, which
is located in the western part of the Chukchi Basin. The Albian-Upper Cretaceous deposits that filled riftogenic zones and
the Paleocene-Lower Neocene rocks that formed under the conditions of continuing spreading make up the sedimentary cover,
which has undergone substantial deformation because of strike-slip motions. As a result of paleoreconstructions, the principal
period of formation for this structure was determined as the Paleocene-Late Miocene, when strike-slip motions of blocks beneath
the South Chukchi Basin occurred. 相似文献
13.
DOUGLAS I. BENN 《Sedimentology》1995,42(5):735-747
The foreland of Breidamerkurjökull, Iceland, is the only locality where tills known to have undergone subglacial deformation are exposed. Till on the foreland has a two-tiered structure, consisting of a dilatant upper horizon c 0.5 m thick and a compact lower till; these horizons correspond to the ductile deforming A horizon and the brittle-ductile B horizon observed below the glacier by G. S. Boulton and co-workers. The relationship between known strain history and a variety of macrofabric elements is examined for these two genetic facies of deformation till. The upper horizon exhibits variable a-axis fabrics and abundant evidence for clast re-alignment, reflecting ductile flow and rapid clast response to transient strains. In contrast, the lower horizon has consistently well organized a-axis fabrics with a narrow range of dip values, recording clast rotation into parallel with strain axes during brittle or brittle-ductile shear. The data indicate that till strain history imparts identifiable macrofabric signatures, providing important analogues to guide the interpretation of Pleistocene tills. 相似文献
14.
探究青藏高原东南缘构造旋转变形有助于理解青藏高原内部物质向东南方向的挤出过程。目前,有关青藏高原东南缘的构造旋转研究主要针对于两套地层:侏罗系—始新统和中新统—第四系。对侏罗系—始新统研究表明了大范围的顺时针旋转变形的存在,而对中新统—第四系的研究则表明该区域可能同时存在逆时针旋转变形。然而,对这两种构造旋转变形的时间和幅度仍缺乏充分的制约。位于川滇地块的四川盐源盆地同时出露这两套地层。磁性地层研究表明,上新统—中更新统的时代为3.6~0.6 Ma。磁偏角数据揭示上新统—中更新统经历了逆时针旋转变形(-14.4°±2.7°),而古新统—始新统经历了明显的顺时针旋转(10°~21.5°),两套地层间的旋转幅度高达36.6°。鉴于青藏高原东南缘发生大规模顺时针旋转变形的最年轻地层为始新统地层,因此顺时针旋转变形可能发生在始新世—中新世某个时间段。这个时间与红河—哀牢山走滑断裂带的活动时间基本一致,因此顺时针旋转变形可能与该大型断裂带的活动直接相关。盐源盆地记录到的逆时针旋转变形发生于至少3.6 Ma以来,平均旋转速率为4°/Ma。由于磁组构数据表明上新世—中更新世地层并未受到挤压变形作用,因此其逆时针旋转变形可能受周围走滑断裂带的控制。 相似文献
15.
The Dead Sea Basin displays a broad range of salt-related structures that developed in a sinistral strike-slip tectonic environment: en échelon salt ridges, large salt diapirs, transverse oblique normal faults, salt walls and rollovers. Laboratory experiments are used to investigate the mechanics of salt tectonics in pull-apart systems. The results show that in an elongated pull-apart basin the basin fill, although decoupled from the underlying basement by a salt layer, remains frictionally coupled to the boundary. The basin fill, therefore, undergoes a strike-slip shear couple that simultaneously generates en échelon fold trains and oblique normal faults, trending mutually perpendicular. According to the orientation of basin boundaries, sedimentary cover deformation can be dominantly contractional or extensional, at the extremities of pull-apart basins forming either folds and thrusts or normal faults, respectively. These guidelines, applied to the analysis of the Dead Sea Basin, show that the various salt-related structures form a coherent set in the frame of a sinistral strike-slip shearing deformation of the sedimentary basin fill. 相似文献
16.
This paper presents the results of a detailed structural analysis of the northern Nijar and southern Vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the Serrata, Gafarillos and Palomares strike-slip fault zones. These major fault zones control the Neogene deformation of the SE Internal Betic Cordilleras in Spain. Detailed stress analysis on Neogene sediments of the Vera and Nijar basins shows a strike-slip regime with NW–SE-oriented subhorizontal maximum principal stress (σ1) during Tortonian and earliest Messinian times. Under the influence of this stress field, dextral displacement along the N090E-trending Gafarillos fault zone resulted in deformation of the sediments of the southern Sorbas and northeastern Nijar basins. During the early Messinian a clock-wise rotation of the stress field occurred. Stress analysis in rocks with late–early Messinian up to Quaternary ages in the Nijar and Vera basins indicates a strike-slip regime with N–S-oriented subhorizontal maximum principal stress (σ1). Under the influence of this stress field the main activity along the N010E-striking Palomares strike-slip fault zone took place, resulting in deformation of the Neogene sediments of the southeastern Vera basin and culminating in a maximum sinistral displacement of more than 20 km. At the same time the stress field was not suitably oriented to exert a large shear component on the Gafarillos fault zone, which activity ended after the earliest Messinian. Fault and outcrop patterns of syntectonic Neogene sediments in the Vera basin show that displacement along the Palomares fault zone decreased at the end of the Middle Miocene although minor displacement phases may still have occurred during the Late Miocene and possibly even Pliocene. From the Middle Miocene onward, deformation in the Nijar basin was controlled by sinistral displacement along the N040E-trending Serrata strike-slip fault zone. 相似文献
17.
The Aswa Shear Zone (ASZ) is a fundamental Precambrian lithospheric structure that has been shaped by many tectonic events in eastern Africa. It separates the Saharan Metacraton in the northeast from the Northern Uganda terrane (which represents part of the Northeastern Congo block of the Congo craton) to the southwest. Nonetheless, its tectonic evolution is not fully understood. We used high-resolution airborne magnetic and radiometric data over Uganda integrated with Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) in South Sudan to assess the extent, kinematics and contribute to the understanding of the tectonic origin of the ASZ. (1) Our results showed that the ASZ extends in a NW–SE direction for ~ 550 km in Uganda and South Sudan. (2) The airborne magnetic and radiometric data revealed a much wider (~ 50 km) deformation belt than the 5-10 km of the exposed surface expression of the ASZ. The deformation belt is defined by three NW-trending sinistral strike-slip shear zones bounding structural domains with magnetic fabric showing splays of secondary shear zones and shear-related folds. These folds are tighter close to the discrete shear zones with their axial traces becoming sub-parallel to the shear zones. A similar fold pattern is observed in South Sudan from the SRTM DEM. We interpreted these folds as due to ENE–WSW contraction associated with the sinistral strike-slip movement. (3) To the northeast, the magnetic patterns and radiometric signatures suggest the presence of a series of W-verging nappes indicative of strong E–W to NE–SW contraction deformation. (4) We relate the evolution of the ASZ to E–W to NE–SW Neoproterozoic oblique collision between East and West Gondwana. The deformation related to this collision was partitioned into E–W to NE–SW contraction resulting in W-verging thrusts in the east and a sinistral strike-slip movement along the NW-trending ASZ with the strain localized at the boundary between the Saharan Metacraton and the Northern Uganda terrane. 相似文献
18.
论走滑断层作用的几个主要问题 总被引：52，自引：1，他引：52
介绍了走滑断层作用研究前缘的若干主要方面。认为普遍使用走滑断层的术语外，在大陆上当断层性质不明时可使用平移断层。强调了单剪机制对大型走滑断层形成的作用，并评论了Ｘ破裂的纯剪理论。基于我国郯庐断裂带等的研究成果，提出走滑断层作用的若干新概念。指出剪曲（牵引）构造不同于雁列褶皱。认为中国地质学家从地质力学研究走滑断层的旋转构造已有卓绝的成就，只要同世界科学接轨，就会获得新的巨大生命力。文中描述了确定位移的方法，提出平移幅度与错距是两个不同的概念。强调了剪切热在大陆构造中的作用，提出走滑剪切带演化中剪切变形－断裂动热变质－重熔岩浆作用旋回。讨论了剪切成矿作用及已成矿体、矿带的走滑错移及变形。划分了三种基本走滑盆地类型及论证了大陆浅源走滑型地震机制。 相似文献
19.
右江地区北西向断裂起源于晚古生代右江盆地内发育的同沉积断裂，这些断裂近等间距平行分布，新生代以来发生了多期次左旋走滑活动，进而导致了右江地区整体发生简单剪切变形。利用三维沙箱模型展开了物理模拟实验，对新生代右江地区的变形机制进行了分析。实验结果表明，早期在红河断裂的左旋剪切错动和印支地块的顺时针旋转联合作用下，右江地区北西向断裂复活，并发生明显的左旋走滑活动；随后川滇地块发生东南向的挤出运动，对右江地区产生侧向挤压，导致了右江地区北西向断裂新一轮的快速左旋走滑活动，同时还导致了右江地区西部的地壳压缩增厚。实验证实新生代右江地区的简单剪切变形以及北西向断裂的走滑活动是印支地块和川滇地块挤出运动共同作用的结果，同时也是印度-欧亚板块碰撞产生的连锁反应之一。 相似文献
20.
slaug Geirsdttir Jrunn Hardardttir rny E. Sveinbjrnsdttir 《Quaternary Science Reviews》2000,19(17-18)
Reconstruction of the paleoenvironment of South Iceland based on lithofacies and chronological studies of the Búdi morainal complex, lacustrine deposits at Ófærugil and a sediment core from Lake Hestvatn, South Iceland, revealed evidence for repeated catastrophic flood (jökulhlaup) activities during the late Younger Dryas (YD) and the early Preboreal (PB) chronozones. During this time, thin and lobate outlet glaciers from the retreating Iceland Ice Cap extended from major valleys and calved into the paleobay of southern lowlands of Iceland where relative sea level was at least 70 m higher than today. A number of ice-marginal lakes formed during the stepwise retreat of the South Iceland ice sheet at the transition of the YD and PB. Primary geomorphic and sedimentologic impact of the jökulhlaups was erosion of multiple channels downstream from the most prominent moraines in South Iceland and through the coastal sediment, accompanied by net aggradation of chaotically stratified sand and silt lenses. At the ice-distal environment, these floods accumulated in the form of recurrent turbidity currents. Volcanic eruptions, supplemented by a catastrophic release of the ice-marginal lakes, are postulated as the main triggers for the jökulhlaup activity. The jökulhlaup events evidenced in this study and subsequent break-up of the partly marine-based glacier may have contributed to the ice-rafting events found in the North Atlantic paleoenvironmental record. 相似文献